Sewing machine structures and garment feeding mechanisms have taken a variety of configurations over the years since their initial conception. Today, the general configuration of the sewing machine comprises a needle assembly, including a needle and presser foot, being driven by a shaft and a feed mechanism to move a garment past the needle assembly as it reciprocates. Traditionally, the feed mechanism takes the form of "feed dogs", i.e., elongated members located beneath the needle having serrated upper surfaces for engaging the garment and moving it toward the needle. The drive mechanism for the feed dogs is typically interconnected with the needle assembly drive mechanism so that the feed dogs do not push the garment while engaged with the needle.
This system, however, is unreliable when the material thickness of adjacent portions of a single garment varies greatly. This differs from a puller device that can accommodate varying thicknesses of different garments but where each individual garment has only one material thickness. For example, the commercial fabrication of heavy jean slacks requires a thirteen ply thickness to be sewn under one presser foot and a four ply thickness to be sewn under another presser foot, as opposed to the fabrication of a garment having a uniform thickness. Using traditional puller mechanisms, the puller rollers either slow down, stop completely or slip, causing the variable thickness garment to feed improperly.
The prior art discloses an upper and lower roller which engage a garment behind a single presser foot: U.S. Pat. No. 2,687,704, Galkin, issued Aug. 31, 1954; U.S. Pat. No. 2,706,457, Galkin, issued Apr. 19, 1995; U.S. Pat. No. 4,187,795, Norton, issued Feb. 12, 1980; U.S. Pat. No. 4,318,360, Uemura et al., issued Mar. 9, 1982. One of the rollers is driven so as to impart motion to the material, along with the feed dog, when the needle is withdrawn. The force of the presser foot on the material overcomes the driving force of the rollers during that portion of the operational cycle when the feed dog disengages the material. When the feed dog engages the material, thereby pushing it, the drive roller rotates to assist in the material feed. The prior art cannot properly accommodate a single garment having adjacent portions of variable thickness fabric since the upper and lower rollers would only engage the greatest fabric thickness while leaving the thinner fabric thickness to pass uncontrolled through the stitch-forming mechanism. None of the aforesaid patents disclose a device for uniformly feeding a single garment, wherein the material thickness of adjacent portions of the garment varies greatly.
The prior art also discloses a single roller positioned substantially below the sewing machine work surface and behind a single presser foot, U.S. Pat. No. 3,198,153, Weber, issued Aug. 3, 1965. Similarly, the prior art discloses a single roller positioned substantially above the sewing machine work surface and behind a single presser foot: U.S. Pat. No. 3,625,168, Palazzo, issued Dec. 7, 1971; U.S. Pat. No. 4,996,934, Lue, issued Mar. 5, 1991. None of these patent, however, disclose a puller device that can properly accommodate a single garment having adjacent portions of variable fabric.
Another deficiency of the prior art is the inability to cut excess threads from a variable thickness fabric after being moved by a roller. For example, U.S. Pat. No. 4,461,229, Angele, issued Jul. 24, 1984, discloses a roller that operates behind a needle assembly to pull a garment in order to cut thread from the garment. However, the puller wheel is positioned such that it interferes with the thread cutting process. In addition, the puller wheel is manually engaged by a lever, which further interferes with the cutting process. A puller device which allows excess threads to be cut from the garment without adjusting for the interference of the puller device is not disclosed. A solution would be to provide a puller roller positioned so as not to interfere with the thread cutting process.
Another deficiency of the aforesaid prior art is that the puller device is disclosed to be driven by the sewing machine motor. Therefore, any adjustment or repair of the puller device requires downtime of the sewing machine in order to adjust the puller roller's speed, maintain the puller roller support beatings or repair the puller device.